Here's what Guy Kawasaki, CEO of Garage Technology Ventures, has to say in his Forbes.com column:
The party that owns 51% of a company does not control it, other than on paper--and, maybe, in their minds. The moment you take $1 from outside investors, you are working for them. At the end of the day, your dream should be to hold 5% to 7% of a huge company, not 51% of a trivial one. To build a huge company, you do what you have to do, including bringing in investors who can help you. These investors will require a larger ownership than your, individual one.